Method, apparatus and program product for predicting multiaxial fatigue life

ABSTRACT

A method for predicting a multiaxial fatigue life. The method includes: obtaining a first temperature rise value of a to-be-tested material in a first cycle; determining first inherent dissipation energy of the to-be-tested material in the first cycle according to the first temperature rise value and a time constant; and determining the multiaxial fatigue life of the to-be-tested material according to a first proportional value, the first inherent dissipated energy, axial fatigue test parameters and torsional fatigue test parameters; the first proportional value is a ratio of an axial strain amplitude to a torsional strain amplitude of a multiaxial fatigue test, the axial fatigue test parameters are configured to represent an axial fatigue resistance of the to-be-tested material, and the torsional fatigue test parameters are configured to represent a torsional fatigue resistance of the to-be-tested material.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a U.S. National Stage of InternationalApplication No. PCT/CN2020/106873, filed on Aug. 4, 2020, the contentsof all of which are incorporated herein by reference in their entiretiesfor all purposes.

BACKGROUND

In engineering practice, most materials and structures in the fields ofautomobiles, high-speed trains, and steam turbines actually bear fatigueloads, most of materials and structures either directly bear multiaxialfatigue loads or are in the states of multiaxial stress and strain atthe local defective and non-continuous positions, which eventuallymanifests as multiaxial fatigue failure. In view of the fact thatmultiaxial fatigue is closer to the real service conditions of materialsand structures, the research on multiaxial fatigue is very important,and the prediction of multiaxial fatigue life of materials is the core.

SUMMARY

A first aspect of the disclosure provides a method for predictingmultiaxial fatigue life, including:

obtaining a first temperature rise value of a to-be-tested material in afirst cycle;

determining first inherent dissipated energy (also referred to as firstdissipated energy) of the to-be-tested material in the first cycleaccording to the first temperature rise value and a time parameter value(also referred to as time constant); and

determining a multiaxial fatigue life of the to-be-tested materialaccording to a first proportional value, the first inherent dissipatedenergy, axial fatigue test parameters (also referred to tensionalfatigue parameters) and tangential fatigue test parameters (alsoreferred to torsional fatigue parameters); and the first proportionalvalue is a ratio of an axial (also referred to tensional) strainamplitude to a tangential(also referred to torsional) strain amplitudeof a multiaxial fatigue test, the axial fatigue test parameters areconfigured to represent an axial fatigue resistance of the to-be-testedmaterial, and the torsional fatigue test parameters are configured torepresent a torsional fatigue resistance of the to-be-tested material.

A second aspect of the disclosure provides an electronic device,including:

a memory, storing a computer program; and

a processor, configured to execute the computer program in the memory toimplement the steps of any method in the first aspect.

In a third aspect, the disclosure provides a non-transitory computerreadable storage medium, storing a computer program thereupon. When thecomputer program in the storage medium is executed by a processor, theprocessor is caused to implement the steps of any method in the firstaspect.

Other features and advantages of the disclosure will be described indetail in the subsequent detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are intended to provide a furtherunderstanding of the disclosure, form a part of the description, and areused to explain the disclosure together with the following detaileddescription, but do not constitute a limitation to the disclosure. Inthe accompanying drawings:

FIG. 1 is a schematic structural diagram of a system for predictingmultiaxial fatigue life illustrated according to an example.

FIG. 2 is a flow diagram of a method for predicting multiaxial fatiguelife illustrated according to an example.

FIG. 3 is a flow diagram of a method for determining axial fatigue testparameter illustrated according to an example.

FIG. 4 is a flow diagram of a method for determining torsional fatiguetest parameter illustrated according to an example.

FIG. 5 is a schematic diagram of a relationship between inherentdissipated energy and a fatigue life in uniaxial tension-compressionfatigue and pure torsional fatigue illustrated according to an example.

FIG. 6 is a schematic diagram of a load path illustrated according to anexample.

FIG. 7 is a comparison diagram of a multiaxial fatigue life predictionresult and an experimental life result illustrated according to anexample.

FIG. 8 is a block diagram of an apparatus for predicting multiaxialfatigue life illustrated according to an example.

FIG. 9 is a block diagram of another apparatus for predicting multiaxialfatigue life illustrated according to an example.

FIG. 10 is a block diagram of an electronic device illustrated accordingto an example.

DETAILED DESCRIPTION

The detailed description of the disclosure is described in detail belowin combination with the accompanying drawings. It should be understoodthat the detailed description described herein is only used toillustrate and explain the disclosure and are not used to limit thedisclosure.

The disclosure relates to the technical field of fatigue failure, inparticular to a method and apparatus for predicting multiaxial fatiguelife, and a program product.

In engineering practice, most materials and structures in the fields ofautomobiles, high-speed trains, and steam turbines actually bear fatigueloads, most of materials and structures either directly bear multiaxialfatigue loads or are in the states of multiaxial stress and strain atthe local defective and non-continuous positions, which eventuallymanifests as multiaxial fatigue failure. In view of the fact thatmultiaxial fatigue is closer to the real service conditions of materialsand structures, the research on multiaxial fatigue is very important,and the prediction of multiaxial fatigue life of materials is the core.

A current method for predicting the multiaxial fatigue life of materialsis usually to obtain the stress and strain states during the multiaxialfatigue test of the materials, and then use the stress and strain statesbe equivalent to the uniaxial fatigue damage parameter, for example, thestress and strain states of brittleness material are equivalent to theaxial fatigue damage parameter, and the stress and strain states oftoughness material are equivalent to the torsional fatigue damageparameter, and then a relationship between the fatigue damage parameterand the fatigue life is established according to the uniaxial fatiguetest, and then the multiaxial fatigue life of the materials is obtainedaccording to the equivalent fatigue damage parameter.

However, the uniaxial fatigue damage parameter can only represent theaxial or torsional uniaxial fatigue resistance. For some materials withsignificantly different axial and torsional fatigue resistances, theuniaxial fatigue damage parameter cannot fully consider the influence ofthe axial and torsional fatigue resistance on the materials, and thus,the applicability of equivalent uniaxial-based multiaxial fatigue lifeprediction methods to different materials is limited.

FIG. 1 is a schematic structural diagram of a system for predictingmultiaxial fatigue life illustrated according to an example. As shown inFIG. 1 , the system includes: a controller 101, a fatigue testingmachine 102, a temperature sensor 103 and a to-be-tested material 104.The controller 101 is connected to the fatigue testing machine 102 andthe temperature sensor 103 respectively, and the to-be-tested material104 is connected to the fatigue testing machine 102 and the temperaturesensor 103 separately.

In this example, the fatigue testing machine 102 is configured toperform a multiaxial fatigue test on the to-be-tested material 104according to a fixed frequency cycle with a ratio of an axial strainamplitude to a torsional strain amplitude being a first proportionalvalue. For example, black matte paint may be sprayed on the surface ofthe to-be-tested material 104 in advance to increase the thermalemissivity of the surface of the to-be-tested material 104, and theto-be-tested material 104 is fixedly installed on the fatigue testingmachine 102 through a fixture.

The temperature sensor 103 is configured to obtain a surface temperatureof the to-be-tested material 104 during the cyclic loading of strain bythe fatigue testing machine 102 at an ultra-high loading frequency,e.g., a frequency of 20 kHz. In some examples, the temperature sensormay be an infrared camera, and the infrared camera may realizereal-time, non-contact, non-destructive and high-sampling-frequencytemperature acquisition of the to-be-tested material 104. Further, afterthe infrared camera is erected, the position of the infrared camera isadjusted so that a thermal image of the to-be-tested material 104 is ina field of view of the infrared camera.

The controller 101 is configured to determine a multiaxial fatigue lifeof the to-be-tested material according to the first proportional valueand the surface temperature, collected by the temperature sensor, of theto-be-tested material 104.

The following describes how the multiaxial fatigue life predictingsystem provided by the disclosure tests the multiaxial fatigue life withreference to specific examples.

FIG. 2 is a flow diagram of a method for predicting multiaxial fatiguelife illustrated according to an example. As shown in FIG. 2 , themethod includes:

S201, a first temperature rise value of a to-be-tested material in afirst cycle is obtained.

In this example, the fatigue testing machine is controlled to perform amultiaxial fatigue test on the to-be-tested material according to afixed frequency with a ratio of an axial (also referred to tensional)strain amplitude to a tangential (also referred to torsional) strainamplitude being a first proportional value. Before starting themultiaxial fatigue test, the infrared camera is controlled to collect anaverage value of a temperature of a target region on the surface of theto-be-tested material as a first temperature.

Further, after the multiaxial fatigue test is started, an average valueof the temperature of the target region on the surface of theto-be-tested material in each cycle is collected as a secondtemperature, and then the first temperature rise value of the targetregion on the surface of the to-be-tested material in each cycle isdetermined according to a difference between the second temperature andthe first temperature. For example, the target region is a region wherethe surface strain of the to-be-tested material is the largest, and isalso a dangerous section of the to-be-tested material.

Further, after the first temperature rise value of the surface of theto-be-tested material in each cycle is obtained, if the differencebetween the first temperature rise values of the surface of theto-be-tested material in two consecutive cycles is less than a presetthreshold, any one of the two consecutive cycles is taken as the firstcycle, and the first temperature rise value of the surface of theto-be-tested material in the first cycle is obtained.

S202, first inherent dissipated energy (also referred to firstdissipated energy) of the to-be-tested material in the first cycle isdetermined according to the first temperature rise value and a timeparameter value (also referred to time constant).

Further, after the first temperature rise value of the target region onthe surface of the to-be-tested material in each cycle is determined,according to a duration of each cycle and the first temperature risevalue of the target region on the surface of the to-be-tested materialin each cycle, a corresponding relationship between the firsttemperature rise value and time is determined, that is, a correspondingfunctional relationship between the first temperature rise value and thetime.

Then the first inherent dissipated energy is determined according to thecorresponding relationship between the first temperature rise value andthe time, the time constant, and a density and a specific heat capacityof the to-be-tested material.

For example, a formula for calculating the inherent dissipated energy isshown in formula (1):

$\begin{matrix}{{\rho{C\left( {\frac{\partial\theta}{\partial t} + \frac{\theta}{\tau_{eq}}} \right)}} = d_{1}} & (1)\end{matrix}$

where, ρ is the density of the to-be-tested material, C is the specificheat capacity of the to-be-tested material; θ is the temperature risevalue; d₁ is the inherent dissipated energy; t is the time; and τ_(eq)is the time constant, which is a time dimension parameter, τ_(eq)characterizes the heat loss. For example, the first temperature risevalue of the surface of the to-be-tested material in the first cycle issubstituted into θ, the corresponding relationship between the firsttemperature rise value and the time is substituted into

$\frac{\partial\theta}{\partial t},$

the value oft is the duration of the first cycle, and then the firstinherent dissipated energy may be calculated according to formula (1).

S203, a multiaxial fatigue life of the to-be-tested material isdetermined according to the first proportional value, the first inherentdissipated energy, axial fatigue test parameters (also referred totensional fatigue parameters) and tangential fatigue test parameters(also referred to torsional fatigue parameters).

In this example, the first proportional value is a ratio of an axialstrain amplitude to a torsional strain amplitude of the multiaxialfatigue test. The axial fatigue test parameters are configured torepresent an axial fatigue resistance of the to-be-tested material, andthe torsional fatigue test parameters are configured to represent atorsional fatigue resistance of the to-be-tested material. The axialfatigue test parameters may be obtained by performing an axial fatiguetest on the to-be-tested material. For example, the axial fatigue testis a uniaxial tension-compression fatigue test. The torsional fatiguetest parameters may be obtained by performing a torsional fatigue teston the to-be-tested material. For example, the torsional fatigue test isa pure torsion fatigue test.

For example, a formula for calculating the multiaxial fatigue life isshown in formula (2):

N _(f,p)=(1−k)·N _(f,A) +k·N _(f,T)  (2)

where, N_(f,p) is the multiaxial fatigue life; N_(f,A) is the axialfatigue life under the same equivalent strain; N_(f,T) is the torsionalfatigue life under the same equivalent strain; and k is a weightcoefficient, a value range of the weight coefficient is 0≤k≤1, aspecific value is determined by the ratio of the axial strain amplitudeto the torsional strain amplitude of the multiaxial fatigue test, and anexpression of k is shown in formula (3):

$\begin{matrix}{k = {\frac{2}{\pi}ac{\tan\left( \frac{\lambda}{\sqrt{3}} \right)}}} & (3)\end{matrix}$

where, λ is the ratio of the axial strain amplitude to the torsionalstrain amplitude of the multiaxial fatigue test, that is, a first ratio,a value range of the first ratio is 0-∞, and a value range correspondingto k is 0-1. In particular, when λ=√{square root over (3)}, k=0.5, whichrepresents the multiaxial fatigue life under the multiaxial fatiguecondition and is an average superposition of the uniaxialtensile-compression fatigue life N_(f,A) and the pure torsional fatiguelife N_(f,T) under the same equivalent strain.

The axial fatigue resistance and the torsional fatigue resistance may berepresented by the axial fatigue test parameters and the torsionalfatigue test parameters respectively. Thus, an axial fatigue strengthcoefficient and an axial fatigue strength exponent of the axial fatiguetest parameters, and a torsional fatigue strength coefficient and atorsional fatigue strength exponent of the torsional fatigue testparameters are substituted into formula (2), and the following formulamay be obtained:

$\begin{matrix}{N_{f,p} = {{\frac{\left( {1 - k} \right)}{D_{A}} \cdot d_{1,{cycle}}^{1/L_{A}}} + {\frac{k}{D_{T}} \cdot d_{1,{cycle}}^{1/L_{T}}}}} & (4)\end{matrix}$

where, d_(1, cycle) is the first inherent dissipated energy calculatedby formula (1). D_(A) is equivalent to the axial fatigue strengthcoefficient, D_(T) is equivalent to the torsional fatigue strengthcoefficient, L_(A) is equivalent to the axial fatigue strength exponent,and L_(T) is equivalent to the torsional fatigue strength exponent.Further, both D_(A) and L_(A) are the axial fatigue test parameters,which may be configured to represent the axial fatigue resistance of theto-be-tested material. Both D_(T) and L_(T) are the torsional fatiguetest parameters, which may be configured to represent the torsionalfatigue resistance of the to-be-tested material. D_(A) and L_(A) may beobtained by performing the axial fatigue test on the to-be-testedmaterial. D_(T) and L_(T) may be obtained by performing the torsionalfatigue test on the to-be-tested material.

By the above solution, the first temperature rise value of theto-be-tested material in the first cycle may be obtained; the firstinherent dissipated energy of the to-be-tested material in the firstcycle is determined according to the first temperature rise value andthe time constant; and the multiaxial fatigue life of the to-be-testedmaterial is determined according to the first proportional value, thefirst inherent dissipated energy, the axial fatigue test parameters andthe torsional fatigue test parameters. The first proportional value isthe ratio of the axial strain amplitude to the torsional strainamplitude of the multiaxial fatigue test, the axial fatigue testparameters are configured to represent the axial fatigue resistance ofthe to-be-tested material, and the torsional fatigue test parameters areconfigured to represent the torsional fatigue resistance of theto-be-tested material. The tensile-compression fatigue resistance andtorsional fatigue resistance of the to-be-tested material are fullyconsidered, so the method has a wide range of applicability to differentmaterials, and the inherent dissipated energy is used as the fatiguedamage parameter, which may be calculated by temperature data collectedby the temperature acquisition apparatus such as the infrared camera ina real-time and non-contact mode. Therefore, the inherent dissipatedenergy is easy to obtain, which also provides a new idea for onlinedetection and life prediction for equipment in service, the generationof the inherent dissipated energy is accompanied by the fatigue damageevolution process of the to-be-tested material, and the inherentdissipated energy can more accurately represent the fatigue damage stateand evolution process. Thus, the method of the disclosure is adopted,and the accuracy for predicting the multiaxial fatigue life is generallybetter than that of life prediction methods based solely on stress andstrain states.

The following describes how to obtain the axial fatigue test parameterswith reference to specific examples. FIG. 3 is a flow diagram of amethod for determining axial fatigue test parameter illustratedaccording to an example. As shown in FIG. 3 , the method includes:

S301, the axial fatigue test is performed on the to-be-tested materialuntil fatigue failure occurs in the to-be-tested material, and an axialfatigue life of the to-be-tested material is determined.

In this example, the axial fatigue test is performed on the to-be-testedmaterial, a first strain amplitude of the axial fatigue test is largerthan a strain amplitude corresponding to an axial fatigue limit of theto-be-tested material, so as to ensure that the to-be-tested materialmay undergo fatigue failure during the axial fatigue test, and a firstaxial fatigue life of the to-be-tested material is determined.

S302, a second temperature rise value of the to-be-tested material in asecond cycle is obtained.

For example, before starting the axial fatigue test on the to-be-testedmaterial, the infrared camera is controlled to collect an average valueof a temperature of a target region on the surface of the to-be-testedmaterial as a third temperature. After the tension-compression fatiguetest is started, an average value of the temperature of the targetregion on the surface of the to-be-tested material in each cycle iscollected as a fourth temperature, and then the second temperature risevalue of the target region on the surface of the to-be-tested materialin each cycle is determined according to a difference between the fourthtemperature and the third temperature. For example, the target region isa region where the surface strain of the to-be-tested material is thelargest, and is also a dangerous section of the to-be-tested material.

Further, after the second temperature rise value of the surface of theto-be-tested material in each cycle is obtained, if the differencebetween the second temperature rise values of the surface of theto-be-tested material in two consecutive cycles is less than a presetthreshold, any one of the two consecutive cycles is taken as the secondcycle, and the second temperature rise value of the surface of theto-be-tested material in the second cycle is obtained.

S303, the axial fatigue test on the to-be-tested material is stoppedafter fatigue failure occurs in the to-be-tested material.

S304, a first duration from fatigue failure occurring in theto-be-tested material to a surface temperature of the to-be-testedmaterial reaching a preset temperature is obtained, and within the firstduration, a corresponding relationship between the temperature risevalues of the to-be-tested material and time is determined according tothe surface temperature of the to-be-tested material.

S305, the time constant is determined according to the first durationand the corresponding relationship between the temperature rise andtime.

For example, after the axial fatigue test on the to-be-tested materialis stopped, no plastic strain occurs inside the to-be-tested material,at this time, the inherent dissipated energy of the to-be-testedmaterial is 0, and the temperature drop on the surface of theto-be-tested material is completely caused by the heat exchange betweenthe to-be-tested material and the external environment, and thus, afterthe fatigue test is stopped, an integral over time of the inherentdissipated energy obtained according to formula (1) is 0, and acalculation formula of the integral is as follows:

$\begin{matrix}\left\{ \begin{matrix}{{R\left( \tau_{eq} \right)} = {\int\limits_{\Gamma}{{s\left( {t,\tau_{eq}} \right)}^{2}{dt}}}} \\{{\frac{\partial R}{\partial\tau_{eq}}❘_{\tau_{eq} = \tau_{opt}}} = 0}\end{matrix} \right. & (5)\end{matrix}$

where, R(τ_(eq)) is the quadratic integral of the inherent dissipatedenergy within the first duration, and R(τ_(eq)) is a function of t.

$\frac{\partial\theta}{\partial t}$

and θ may be obtained from the corresponding relationship between thetemperature rise values of the to-be-tested material and the time. Then

$\frac{\partial\theta}{\partial t}$

is substituted into formula (1), and quadratic integration is performedon formula (1) with time to obtain R(τ_(eq)).

In formula (5), Γ is the first duration from fatigue failure occurringthe to-be-tested material to the surface temperature of the to-be-testedmaterial dropping to the preset temperature, and the preset temperatureis a third temperature.

Further, after the fatigue test is stopped, the integral over time ofthe inherent dissipated energy is 0, so

$\frac{\partial R}{\partial\tau_{eq}}$

is 0, and when a value of the time constant τ_(eq) is τ

,

$\frac{\partial R}{\partial\tau_{eq}}$

is 0, so the value of the time constant τ_(eq) is τ

.

S306, second inherent dissipated energy of the material in the secondcycle is determined according to the second temperature rise value andthe time constant.

Further, after it is determined that the value of the time constantτ_(eq) is τ

, then the second temperature rise value, τ

,

$\frac{\partial\theta}{\partial t}$

and a duration of the second cycle are substituted into formula (1), soas to obtain the second inherent dissipated energy in the second cycle.

S307, the axial fatigue strength coefficient and the axial fatiguestrength exponent of the to-be-tested material are determined accordingto the second inherent dissipated energy and the axial fatigue life.

Further, according to the time from the start of the axial fatigue teston the to-be-tested material to the fatigue failure occurring in theto-be-tested material, the total quantity of cycles is the first axialfatigue life of the to-be-tested material under the first strainamplitude.

For example, an amplitude value of the first strain amplitude isincreased according to a preset increment amplitude value to obtain asecond strain amplitude value, and then the axial fatigue test on theto-be-tested material is started according to the second strainamplitude value until fatigue failure occurs, a second axial fatiguelife of the to-be-tested material is determined, and in the same manner,the second inherent dissipated energy at the second strain amplitudevalue is calculated.

In the same way, until the axial fatigue test on the to-be-testedmaterial is started according to a fifth strain amplitude value untilfatigue failure occurs, a fifth axial fatigue life of the to-be-testedmaterial is determined, and the second inherent dissipated energy at thefifth strain amplitude value is calculated. Then, the second inherentdissipated energy under the first to fifth strain amplitude values andthe first to fifth axial fatigue lives are fitted in a preset coordinatesystem, and an obtained curve is shown in formula (6):

d _(1,A) =D _(A)·(N _(A))^(L) ^(A)   (6)

where, d_(1, A) is the second inherent dissipated energy, a fittingcoefficient D_(A) is the axial fatigue strength coefficient, and afitting exponent L_(A) is the axial fatigue strength exponent.

Through the above solution, the axial fatigue test may be performed onthe to-be-tested material, after the to-be-tested material has fatiguefailure, the time constant is determined, and then the second inherentdissipated energy is determined according to the time constant, and thenthe axial fatigue strength coefficient and the axial fatigue strengthexponent of the to-be-tested material are determined according to thecorresponding relationship between the second dissipated energy and theaxial fatigue life.

The following describes how to obtain the torsional fatigue testparameters with reference to specific examples. FIG. 4 is a flow diagramof a method for determining torsional fatigue test parameter illustratedaccording to an example. As shown in FIG. 4 , the method includes:

S401, the torsional fatigue test is performed on the to-be-testedmaterial until fatigue failure occurs in the to-be-tested material, anda torsional fatigue life of the to-be-tested material is determined.

In this example, the torsional fatigue test is performed on theto-be-tested material, a first strain amplitude of the torsional fatiguetest is larger than a strain amplitude corresponding to a torsionalfatigue limit of the to-be-tested material, so as to ensure that theto-be-tested material may undergo fatigue failure during the torsionalfatigue test, and a first torsional fatigue life of the to-be-testedmaterial is determined.

S402, a third temperature rise value of the to-be-tested material in athird cycle is obtained.

For example, before starting the torsional fatigue test on theto-be-tested material, the infrared camera is controlled to collect anaverage value of a temperature of a target region on the surface of theto-be-tested material as a fifth temperature. After the torsionalfatigue test is started, an average value of the temperature of thetarget region on the surface of the to-be-tested material in each cycleis collected as a sixth temperature, and then the third temperature risevalue of the target region on the surface of the to-be-tested materialin each cycle is determined according to a difference between the sixthtemperature and the fifth temperature. For example, the target region isa region where the surface strain of the to-be-tested material is thelargest, and is also a dangerous section of the to-be-tested material.

Further, after the third temperature rise value of the surface of theto-be-tested material in each cycle is obtained, if the differencebetween the third temperature rise values of the surface of theto-be-tested material in two consecutive cycles is less than a presetthreshold, any one of the two consecutive cycles is taken as the thirdcycle, and the third temperature rise value of the surface of theto-be-tested material in the third cycle is obtained.

S403, third inherent dissipated energy of the to-be-tested material inthe third cycle is determined according to the third temperature risevalue and the time constant.

Further, after the third temperature rise value of the target region onthe surface of the to-be-tested material in each cycle is determined,according to a duration of each cycle and the third temperature risevalue of the target region on the surface of the to-be-tested materialin each cycle, a corresponding relationship between the thirdtemperature rise value and time is determined, that is, a correspondingfunctional relationship between the third temperature rise value and thetime.

For example, after it is determined that the value of the time constantτ_(eq) is τ

in step S304, τ

, the third temperature rise value, and the corresponding functionalrelationship between the third temperature rise value and the time aresubstituted into formula (1), so as to obtain the third inherentdissipated energy in the third cycle.

S404, the torsional fatigue strength coefficient and the torsionalfatigue strength exponent of the to-be-tested material are determinedaccording to the third inherent dissipated energy and the torsionalfatigue life.

Further, according to the time from the start of the torsional fatiguetest on the to-be-tested material to the fatigue failure occurring inthe to-be-tested material, the quantity of cycles from the start of thetorsional fatigue on the to-be-tested material is the first torsionalfatigue life of the to-be-tested material under the first strainamplitude.

For example, the amplitude value of the first strain amplitude isincreased according to the preset increment amplitude value to obtainthe second strain amplitude value, and then the torsional fatigue teston the to-be-tested material is started according to the second strainamplitude value until fatigue failure occurs, a second torsional fatiguelife of the to-be-tested material is determined, and in the same manner,the third inherent dissipated energy at the second strain amplitudevalue is calculated.

In the same way, until the torsional fatigue test on the to-be-testedmaterial is started according to the fifth strain amplitude value untilfatigue failure occurs, a fifth torsional fatigue life of theto-be-tested material is determined, and the third inherent dissipatedenergy at the fifth strain amplitude value is calculated. Then, thethird inherent dissipated energy under the first to fifth strainamplitude values and the first to fifth torsional fatigue lives arefitted in a preset coordinate system, and an obtained curve is shown informula (7):

d _(1,T) =D _(T)·(N _(T))^(L) ^(T)   (7)

where, d_(1,T) is the third inherent dissipated energy, a fittingcoefficient D_(T) is the torsional fatigue strength coefficient, and afitting exponent L_(T) is the torsional fatigue strength exponent.

Through the above solution, the torsional fatigue test may be performedon the to-be-tested material, the third inherent dissipated energy inthe third cycle in the torsional fatigue test process is determined, andthen the torsional fatigue strength coefficient and the torsionalfatigue strength exponent of the to-be-tested material are determinedaccording to the corresponding relationship between the third dissipatedenergy and the torsional fatigue life.

In order to illustrate the detailed description of the method of thedisclosure more concretely, the following takes a group of 316Lstainless steel as the to-be-tested material as an example to describehow the disclosure predicts the multiaxial fatigue life.

First, black matte paint is sprayed on the surface of a 316L stainlesssteel sample to improve the thermal emissivity of the surface of thesample, so as to ensure the accuracy of temperature acquisition by theinfrared camera. The infrared camera is erected, and the position of theinfrared camera is adjusted so that a parallel section of the sample isright in a field of view of the infrared camera. Further, non-uniformcorrection is performed on the infrared camera, and a temperatureacquisition range and a sampling frequency of the infrared camera areset.

Secondly, an appropriate loading strain amplitude value is selected, anda set of uniaxial tension-compression fatigue tests with 5 differentstrain amplitude values and a set of pure torsional fatigue tests with 5different strain amplitude values are performed. During each fatiguetest, the thermal imager is first turned on to collect the temperature,and then starts the fatigue test, and the temperature field data of thesample during the fatigue test are collected in real time. When thefatigue failure occurs in the sample, the fatigue test ends, and whenthe temperature of the sample cools down to a near room temperature, thetemperature acquisition of the thermal imager is stopped.

According to the temperature field data collected in the fatigue test,the formula (1) is used to calculate the second inherent dissipatedenergy of all the uniaxial tension-compression fatigue tests and thethird inherent dissipated energy of the pure torsional fatigue tests.

A plurality of second inherent dissipative energies and axial fatiguelives correspond to each other, and a plurality of third inherentdissipative energies and torsional fatigue lives correspond to eachother, and according to the forms of formula (6) and formula (7),inherent dissipated energy and fatigue life equations under the uniaxialtension-compression fatigue and the pure torsional fatigue areestablished, respectively:

d _(1,A)=2.34×10⁸·(N _(A))^(−0.53)  (8)

d _(1,T)=1.50×10⁸·(N _(T))^(−0.42)  (9)

that is, the fitting coefficients D_(A)=2.34×10⁸, D_(T)=1.50×10⁸, thefitting exponent L_(A)=−0.53, L_(T)=−0.42, the fitting relationship isshown in FIG. 5 , and FIG. 5 is a schematic diagram of a relationshipbetween inherent dissipated energy and a fatigue life under uniaxialtension-compression fatigue and pure torsional fatigue illustratedaccording to an example. D_(A), D_(T), L_(A) and L_(T) are substitutedinto formula (4), and a formula for calculating the multiaxial fatiguelife of the material based on the dissipated energy may be obtained:

$\begin{matrix}{N_{f,p} = {{\frac{\left( {1 - k} \right)}{2.34 \times 10^{8}} \cdot d_{1,{cycle}}^{- 1.89}} + {\frac{k}{1.5 \times 10^{8}} \cdot d_{1,{cycle}}^{- 2.38}}}} & (10)\end{matrix}$

where, the weight coefficient

$k = {\frac{2}{\pi}ac{\tan\left( \frac{\lambda}{\sqrt{3}} \right)}}$

is only related to the ratio λ of the axial strain amplitude to thetorsional strain amplitude of the multiaxial fatigue test. When themultiaxial fatigue life prediction is performed on the to-be-testedmaterial, the ratio λ of the axial strain amplitude to the torsionalstrain amplitude is determined, only the first inherent dissipatedenergy d_(1,cycle) in the first cycle when the multiaxial fatigue testis performed on the to-be-tested material needs to be determined and issubstituted into formula (10), and the multiaxial fatigue life under themultiaxial fatigue test condition may be estimated. Next, the accuracyof predicting the multiaxial life by formula (10) is verified.

In this example, when the fatigue test is performed on the to-be-testedmaterial to verify the accuracy of formula (10), in addition to auniaxial tension-compression load path and a pure torsional load path,three other multiaxial load paths are selected, which are a proportionalload path, a 45° non-proportional load path, and a 90° non-proportionalload path, and all 5 load paths are shown in FIG. 6 . FIG. 6 is aschematic diagram of a load path illustrated according to an example.For each load path, 5 to 6 different loading strain amplitudes areselected for fatigue test, the surface temperature change of the samplein the fatigue process is collected at the same time, and formula (1) isadopted to calculate the first inherent dissipated energy in the firstcycle.

A comparison relationship between multiaxial fatigue life predictionresults under five load paths and experimental lives by using the methodof the disclosure is shown in FIG. 7 . FIG. 7 is a comparison diagram ofa multiaxial fatigue life prediction result and an experimental liferesult illustrated according to an example. A black diagonal line in thefigure represents an ideal result equal to the multiaxial fatigue lifeobtained from the experiment, dotted lines indicate that the multiaxialfatigue life predicted according to formula (10) and the multiaxialfatigue life obtained by the experiment are within a factor of 2, and arange included by two dotted lines indicates that the multiaxial fatiguelife predicted according to formula (10) is 0.5 to 2 times themultiaxial fatigue life obtained by the experiment. Data points in FIG.7 represent the multiaxial fatigue lives predicted by formula (10) underdifferent load paths. When the data points fall within the range of thedotted lines, it indicates that the fatigue life results predictedaccording to formula (10) are ideal. It can be seen from FIG. 7 that alldata points fall within the range of the factor of 2, and most of thedata points are very close to the straight line, or even fall on thestraight line, so the accuracy of predicting the multiaxial fatigue liferesults by the method of the disclosure is very high.

FIG. 8 is a block diagram of an apparatus for predicting multiaxialfatigue life illustrated according to an example. As shown in FIG. 8 ,the apparatus 80 includes:

a temperature rise value obtaining module 801, configured to obtain afirst temperature rise value of a to-be-tested material in a firstcycle;

an inherent dissipated energy determining module 802, configured todetermine first inherent dissipated energy of the to-be-tested materialin the first cycle according to the first temperature rise value and atime constant; and

a multiaxial fatigue life determining module 803, configured todetermine a multiaxial fatigue life of the to-be-tested materialaccording to a first proportional value, the first inherent dissipatedenergy, axial fatigue test parameters and torsional fatigue testparameters; and the first proportional value is a ratio of an axialstrain amplitude to a torsional strain amplitude of a multiaxial fatiguetest, the axial fatigue test parameters are configured to represent anaxial fatigue resistance of the to-be-tested material, and the torsionalfatigue test parameters are configured to represent a torsional fatigueresistance of the to-be-tested material.

In some examples, the axial fatigue test parameters include an axialfatigue strength coefficient and an axial fatigue strength exponent, andthe multiaxial fatigue life determining module 803 is configured to:

perform an axial fatigue test on the to-be-tested material until fatiguefailure occurs in the to-be-tested material, and acquire an axialfatigue life of the to-be-tested material;

obtain a second temperature rise value of the to-be-tested material in asecond cycle;

determine second inherent dissipated energy of the to-be-tested materialin the second cycle according to the second temperature rise value andthe time constant; and

determine the axial fatigue strength exponent and the axial fatiguestrength coefficient of the to-be-tested material according to thesecond inherent dissipated energy and the axial fatigue life.

In some examples, the torsional fatigue test parameters include atorsional fatigue strength exponent and a torsional fatigue strengthcoefficient, and the multiaxial fatigue life determining module 803 isconfigured to:

perform a torsional fatigue test on the to-be-tested material untilfatigue failure occurs in the to-be-tested material, and acquire atorsional fatigue life of the to-be-tested material;

obtain a third temperature rise value of the to-be-tested material in athird cycle;

determine third inherent dissipated energy of the to-be-tested materialin the third cycle according to the third temperature rise value and thetime constant; and

determine the torsional fatigue strength coefficient and the torsionalfatigue strength exponent of the to-be-tested material according to thethird inherent dissipated energy and the torsional fatigue life.

In some examples, FIG. 9 is a block diagram of the apparatus forpredicting multiaxial fatigue life illustrated according to an exampleshown in FIG. 8 . As shown in FIG. 9 , the apparatus 80 furtherincludes:

a fatigue test stopping module 804, configured to stop performing theaxial fatigue test on the to-be-tested material after fatigue failureoccurs in the to-be-tested material;

a corresponding relationship determining module 805, configured toobtain a first duration from fatigue failure occurring in theto-be-tested material to a surface temperature of the to-be-testedmaterial reaching a preset temperature, and within the first duration,determine a corresponding relationship between the temperature risevalues of the to-be-tested material and time according to the surfacetemperature of the to-be-tested material; and

a parameter value determining module 806, configured to determine thetime constant according to the first duration and the correspondingrelationship.

In some examples, the inherent dissipated energy determining module 802is configured to:

determine the first inherent dissipated energy according to the firsttemperature rise value, a second duration of the first cycle, the timeconstant, a density of the to-be-tested material and a specific heatcapacity of the to-be-tested material.

By the above apparatus, the first temperature rise value of theto-be-tested material in the first cycle is obtained; the first inherentdissipated energy of the to-be-tested material in the first cycle isdetermined according to the first temperature rise value and the timeconstant; and the multiaxial fatigue life of the to-be-tested materialis determined according to the first proportional value, the firstinherent dissipated energy, the axial fatigue test parameters and thetorsional fatigue test parameters. The first proportional value is theratio of the axial strain amplitude to the torsional strain amplitude ofthe multiaxial fatigue test, the axial fatigue test parameters areconfigured to represent the axial fatigue resistance of the to-be-testedmaterial, and the torsional fatigue test parameters are configured torepresent the torsional fatigue resistance of the to-be-tested material.The tensile-compression fatigue resistance and torsional fatigueresistance of the to-be-tested material are fully considered, so theapparatus has a wide range of applicability to different materials. Atthe same time, the method uses the dissipated energy released in thefatigue process of the material as a fatigue damage parameter, which maybe calculated by temperature data collected by a temperature acquisitionapparatus such as an infrared camera in a real-time and non-contactmode, so the dissipated energy is easy to obtain and provides a new ideafor online detection and life prediction of equipment in service.

As for the apparatus in the above examples, the specific manner in whicheach module performs operations has been described in detail in theexamples of the method, and detailed description will not be given here.

FIG. 10 is a block diagram of an electronic device 1000 illustratedaccording to an example. Referring to FIG. 10 , the electronic device1000 includes one or more processors 1022, and a memory 1032 configuredto store a computer program executable by the processor 1022. Thecomputer program stored in the memory 1032 may include one or moremodules each corresponding to a set of instructions. In addition, theprocessor 1022 may be configured to execute the computer program toexecute the multiaxial fatigue life predicting method above.

In addition, the electronic device 1000 may further include a powercomponent 1026 and a communication component 1050. The power component1026 may be configured to execute power management of the electronicdevice 1000, and the communication component 1050 may be configured torealize communication of the electronic device 1000, such as wired orwireless communication. In addition, the electronic device 1000 mayfurther include an input/output (I/O) interface 1058. The electronicdevice 1000 may operate an operating system stored in the memory 1032,such as Windows Server™, Mac OS X™, Unix™, Linux™, etc.

In another example, a computer-readable storage medium including programinstructions is further provided. The program instructions, whenexecuted by a processor, implement the steps of the multiaxial fatiguelife predicting method above. For example, the computer-readable storagemedium may be the above memory 1032 including the program instructions,and the above program instructions are executed by the processor 1022 ofthe electronic device 1000 to complete the multiaxial fatigue lifepredicting method above.

In another example, a computer program product is further provided. Thecomputer program product contains a computer program executed by aprogrammable apparatus. The computer program has a code part which isconfigured to, when executed by the programmable apparatus, execute themultiaxial fatigue life predicting method above.

The preferred implementations of the disclosure are described in detailabove in combination with the accompanying drawings. However, thedisclosure is not limited to the specific details of the aboveimplementations. Within the scope of the technical concept of thedisclosure, a variety of simple modifications can be made to thetechnical solutions of the disclosure, and these simple modificationsbelong to the protection scope of the disclosure. In addition, it shouldbe noted that the specific technical features described in the abovedetailed description can be combined in any suitable way withoutcontradiction. In order to avoid unnecessary repetition, variouspossible combinations are not described in the disclosure.

In addition, various different implementations of the disclosure canalso be combined arbitrarily. As long as they do not violate the idea ofthe disclosure, they should also be regarded as the contents disclosedin the disclosure.

1. A method for predicting multiaxial fatigue life, comprising:obtaining a first temperature rise value of a to-be-tested material in afirst cycle; determining first inherent dissipated energy of theto-be-tested material in the first cycle according to the firsttemperature rise value and a time constant; determining a multiaxialfatigue life of the to-be-tested material according to a firstproportional value, the first inherent dissipated energy, axial fatiguetest parameters and torsional fatigue test parameters; wherein the firstproportional value is a ratio of an axial strain amplitude to atorsional strain amplitude of a multiaxial fatigue test, the axialfatigue test parameters are configured to represent an axial fatigueresistance of the to-be-tested material, and the torsional fatigue testparameters are configured to represent a torsional fatigue resistance ofthe to-be-tested material.
 2. The method according to claim 1, whereinthe axial fatigue test parameters comprise an axial fatigue strengthcoefficient and an axial fatigue strength exponent, and the axialfatigue test parameters are obtained by: performing an axial fatiguetest on the to-be-tested material until fatigue failure occurs in theto-be-tested material, and determining an axial fatigue life of theto-be-tested material; obtaining a second temperature rise value of theto-be-tested material in a second cycle; determining second inherentdissipated energy of the to-be-tested material in the second cycleaccording to the second temperature rise value and the time constant;and determining the axial fatigue strength coefficient and the axialfatigue strength exponent of the to-be-tested material according to thesecond inherent dissipated energy and the axial fatigue life.
 3. Themethod according to claim 1, wherein the torsional fatigue testparameters comprise a torsional fatigue strength coefficient and atorsional fatigue strength exponent, and the torsional fatigue testparameters are obtained by: performing a torsional fatigue test on theto-be-tested material until fatigue failure occurs in the to-be-testedmaterial, and determining a torsional fatigue life of the to-be-testedmaterial; obtaining a third temperature rise value of the to-be-testedmaterial in a third cycle; determining third inherent dissipated energyof the to-be-tested material in the third cycle according to the thirdtemperature rise value and the time constant; and determining thetorsional fatigue strength coefficient and the torsional fatiguestrength exponent of the to-be-tested material according to the thirdinherent dissipated energy and the torsional fatigue life.
 4. The methodaccording to claim 2, further comprising: stopping performing the axialfatigue test on the to-be-tested material after fatigue failure occursin the to-be-tested material; obtaining a first duration from fatiguefailure occurring in the to-be-tested material to a surface temperatureof the to-be-tested material reaching a preset temperature, and withinthe first duration, determining a corresponding relationship between thetemperature rise values of the to-be-tested material and time accordingto the surface temperature of the to-be-tested material; and determiningthe time constant according to the first duration and the correspondingrelationship between the temperature rise and time.
 5. The methodaccording to claim 1, wherein the determining the first inherentdissipated energy according to the time constant and the firsttemperature rise value comprises: determining the first inherentdissipated energy according to the first temperature rise value, asecond duration of the first cycle, the time constant, a density of theto-be-tested material and a specific heat capacity of the to-be-testedmaterial. 6.-10. (canceled)
 11. An electronic device, comprising: amemory, storing a computer program thereon; and a processor, configuredto execute the computer program in the memory so as to: obtain a firsttemperature rise value of a to-be-tested material in a first cycle;determine first inherent dissipated energy of the to-be-tested materialin the first cycle according to the first temperature rise value and atime constant; determine a multiaxial fatigue life of the to-be-testedmaterial according to a first proportional value, the first inherentdissipated energy, axial fatigue test parameters and torsional fatiguetest parameters; wherein the first proportional value is a ratio of anaxial strain amplitude to a torsional strain amplitude of a multiaxialfatigue test, the axial fatigue test parameters are configured torepresent an axial fatigue resistance of the to-be-tested material, andthe torsional fatigue test parameters are configured to represent atorsional fatigue resistance of the to-be-tested material. 12.(canceled)
 13. The method according to claim 1, wherein the axialfatigue test parameters comprise an axial fatigue strength coefficientand an axial fatigue strength exponent, the torsional fatigue testparameters comprise a torsional fatigue strength coefficient and atorsional fatigue strength exponent, and a formula for calculating themultiaxial fatigue life is:$N_{f,p} = {{\frac{\left( {1 - k} \right)}{D_{A}} \cdot d_{1,{cycle}}^{1/L_{A}}} + {\frac{k}{D_{T}} \cdot d_{1,{cycle}}^{1/L_{T}}}}$wherein, N_(f,p) is the multiaxial fatigue life, d_(1, cycle) is thefirst inherent dissipated energy, k is a weight coefficient, and k is aspecific value is determined by the ratio of the axial strain amplitudeto the torsional strain amplitude of the multiaxial fatigue test, D_(A)is equivalent to the axial fatigue strength coefficient, D_(T) isequivalent to the torsional fatigue strength coefficient, L_(A) isequivalent to the axial fatigue strength exponent, and L_(T) isequivalent to the torsional fatigue strength exponent.
 14. The methodaccording to claim 2, wherein the torsional fatigue test parameterscomprise a torsional fatigue strength coefficient and a torsionalfatigue strength exponent, and the torsional fatigue test parameters areobtained by: performing a torsional fatigue test on the to-be-testedmaterial until fatigue failure occurs in the to-be-tested material, anddetermining a torsional fatigue life of the to-be-tested material;obtaining a third temperature rise value of the to-be-tested material ina third cycle; determining third inherent dissipated energy of theto-be-tested material in the third cycle according to the thirdtemperature rise value and the time constant; and determining thetorsional fatigue strength coefficient and the torsional fatiguestrength exponent of the to-be-tested material according to the thirdinherent dissipated energy and the torsional fatigue life.
 15. Themethod according to claim 14, wherein a formula for calculating themultiaxial fatigue life is:$N_{f,p} = {{\frac{\left( {1 - k} \right)}{D_{A}} \cdot d_{1,{cycle}}^{1/L_{A}}} + {\frac{k}{D_{T}} \cdot d_{1,{cycle}}^{1/L_{T}}}}$wherein, N_(f,p) is the multiaxial fatigue life, d_(1, cycle) is thefirst inherent dissipated energy, k is a weight coefficient, and k is aspecific value is determined by the ratio of the axial strain amplitudeto the torsional strain amplitude of the multiaxial fatigue test, D_(A)is equivalent to the axial fatigue strength coefficient, D_(T) isequivalent to the torsional fatigue strength coefficient, L_(A) isequivalent to the axial fatigue strength exponent, and L_(T) isequivalent to the torsional fatigue strength exponent.
 16. Theelectronic device according to claim 11, wherein the axial fatigue testparameters comprise an axial fatigue strength coefficient and an axialfatigue strength exponent, and the processor is further configured to:perform an axial fatigue test on the to-be-tested material until fatiguefailure occurs in the to-be-tested material, and acquire an axialfatigue life of the to-be-tested material; obtain a second temperaturerise value of the to-be-tested material in a second cycle; determinesecond inherent dissipated energy of the to-be-tested material in thesecond cycle according to the second temperature rise value and the timeconstant; and determine the axial fatigue strength coefficient and theaxial fatigue strength exponent of the to-be-tested material accordingto the second inherent dissipated energy and the axial fatigue life. 17.The electronic device according to claim 11, wherein the torsionalfatigue test parameters comprise a torsional fatigue strengthcoefficient and a torsional fatigue strength exponent, and the processoris further configured to: perform a torsional fatigue test on theto-be-tested material until fatigue failure occurs in the to-be-testedmaterial, and acquire a torsional fatigue life of the to-be-testedmaterial; obtain a third temperature rise value of the to-be-testedmaterial in a third cycle; determine third inherent dissipated energy ofthe to-be-tested material in the third cycle according to the thirdtemperature rise value and the time constant; and determine thetorsional fatigue strength coefficient and the torsional fatiguestrength exponent of the to-be-tested material according to the thirdinherent dissipated energy and the torsional fatigue life.
 18. Theelectronic device according to claim 16, wherein the processor isfurther configured to: stop performing the axial fatigue test on theto-be-tested material after fatigue failure occurs in the to-be-testedmaterial; obtain a first duration from fatigue failure occurring in theto-be-tested material to a surface temperature of the to-be-testedmaterial reaching a preset temperature, and within the first duration,determine a corresponding relationship between the temperature risevalues of the to-be-tested material and time according to the surfacetemperature of the to-be-tested material; and determine the timeconstant according to the first duration and the correspondingrelationship between the temperature rise and time.
 19. The electronicdevice according to claim 11, wherein the processor is configured to:determine the first inherent dissipated energy according to the firsttemperature rise value, a second duration of the first cycle, the timeconstant, a density of the to-be-tested material and a specific heatcapacity of the to-be-tested material.
 20. The electronic deviceaccording to claim 11, wherein the axial fatigue test parameterscomprise an axial fatigue strength coefficient and an axial fatiguestrength exponent, the torsional fatigue test parameters comprise atorsional fatigue strength coefficient and a torsional fatigue strengthexponent, and a formula for calculating the multiaxial fatigue life is:$N_{f,p} = {{\frac{\left( {1 - k} \right)}{D_{A}} \cdot d_{1,{cycle}}^{1/L_{A}}} + {\frac{k}{D_{T}} \cdot d_{1,{cycle}}^{1/L_{T}}}}$wherein, N_(f,p) is the multiaxial fatigue life, d_(1, cycle) is thefirst inherent dissipated energy, k is a weight coefficient, and k is aspecific value is determined by the ratio of the axial strain amplitudeto the torsional strain amplitude of the multiaxial fatigue test, D_(A)is equivalent to the axial fatigue strength coefficient, D_(T) isequivalent to the torsional fatigue strength coefficient, L_(A) isequivalent to the axial fatigue strength exponent, and L_(T) isequivalent to the torsional fatigue strength exponent.
 21. Anon-transitory computer readable storage medium, storing a computerprogram thereupon, when the computer program in the storage medium isexecuted by a processor, the processor is caused to: obtain a firsttemperature rise value of a to-be-tested material in a first cycle;determine first inherent dissipated energy of the to-be-tested materialin the first cycle according to the first temperature rise value and atime constant; determine a multiaxial fatigue life of the to-be-testedmaterial according to a first proportional value, the first inherentdissipated energy, axial fatigue test parameters and torsional fatiguetest parameters; wherein the first proportional value is a ratio of anaxial strain amplitude to a torsional strain amplitude of a multiaxialfatigue test, the axial fatigue test parameters are configured torepresent an axial fatigue resistance of the to-be-tested material, andthe torsional fatigue test parameters are configured to represent atorsional fatigue resistance of the to-be-tested material.
 22. Thenon-transitory computer readable storage medium according to claim 21,wherein the axial fatigue test parameters comprise an axial fatiguestrength coefficient and an axial fatigue strength exponent, and whenthe computer program in the storage medium is executed by a processor,the processor is further caused to: perform an axial fatigue test on theto-be-tested material until fatigue failure occurs in the to-be-testedmaterial, and acquire an axial fatigue life of the to-be-testedmaterial; obtain a second temperature rise value of the to-be-testedmaterial in a second cycle; determine second inherent dissipated energyof the to-be-tested material in the second cycle according to the secondtemperature rise value and the time constant; and determine the axialfatigue strength coefficient and the axial fatigue strength exponent ofthe to-be-tested material according to the second inherent dissipatedenergy and the axial fatigue life.
 23. The non-transitory computerreadable storage medium according to claim 21, wherein the torsionalfatigue test parameters comprise a torsional fatigue strengthcoefficient and a torsional fatigue strength exponent, and when thecomputer program in the storage medium is executed by a processor, theprocessor is further caused to: perform a torsional fatigue test on theto-be-tested material until fatigue failure occurs in the to-be-testedmaterial, and acquire a torsional fatigue life of the to-be-testedmaterial; obtain a third temperature rise value of the to-be-testedmaterial in a third cycle; determine third inherent dissipated energy ofthe to-be-tested material in the third cycle according to the thirdtemperature rise value and the time constant; and determine thetorsional fatigue strength coefficient and the torsional fatiguestrength exponent of the to-be-tested material according to the thirdinherent dissipated energy and the torsional fatigue life.
 24. Thenon-transitory computer readable storage medium according to claim 22,when the computer program in the storage medium is executed by aprocessor, the processor is further caused to: stop performing the axialfatigue test on the to-be-tested material after fatigue failure occursin the to-be-tested material; obtain a first duration from fatiguefailure occurring in the to-be-tested material to a surface temperatureof the to-be-tested material reaching a preset temperature, and withinthe first duration, determine a corresponding relationship between thetemperature rise values of the to-be-tested material and time accordingto the surface temperature of the to-be-tested material; and determinethe time constant according to the first duration and the correspondingrelationship between the temperature rise and time.
 25. Thenon-transitory computer readable storage medium according to claim 21,when the computer program in the storage medium is executed by aprocessor, the processor is caused to: determine the first inherentdissipated energy according to the first temperature rise value, asecond duration of the first cycle, the time constant, a density of theto-be-tested material and a specific heat capacity of the to-be-testedmaterial.
 26. The non-transitory computer readable storage mediumaccording to claim 21, wherein the axial fatigue test parameterscomprise an axial fatigue strength coefficient and an axial fatiguestrength exponent, the torsional fatigue test parameters comprise atorsional fatigue strength coefficient and a torsional fatigue strengthexponent, and a formula for calculating the multiaxial fatigue life is:$N_{f,p} = {{\frac{\left( {1 - k} \right)}{D_{A}} \cdot d_{1,{cycle}}^{1/L_{A}}} + {\frac{k}{D_{T}} \cdot d_{1,{cycle}}^{1/L_{T}}}}$wherein, N_(f,p) is the multiaxial fatigue life, d_(1, cycle) is thefirst inherent dissipated energy, k is a weight coefficient, and k is aspecific value is determined by the ratio of the axial strain amplitudeto the torsional strain amplitude of the multiaxial fatigue test, D_(A)is equivalent to the axial fatigue strength coefficient, D_(T) isequivalent to the torsional fatigue strength coefficient, L_(A) isequivalent to the axial fatigue strength exponent, and L_(T) isequivalent to the torsional fatigue strength exponent.